高填黄土矩形、拱形明洞减载结构土压力差异性规律研究

Study on Earth Pressure Difference Law of Load Relieving Structure of the Rectangular and Arched High-filled Loess Open Cut Tunnels

  • 摘要: 高填明洞会使结构受力增加,影响结构安全。文章通过模型试验、数值模拟手段,考虑EPS减载、结构截面形式及其基础刚度,研究了明洞洞顶土压力、土体位移随填土高度的变化规律。结果表明,高填明洞减载结构洞顶土压力随填土高度的变化呈非线性变化,拱形截面减载效果优于矩形截面,柔性基础明洞减载效果优于刚性基础;矩形截面从洞顶中心点到两侧的土压力呈现先增大后减小、最后趋于稳定的趋势,在明洞两侧边界处出现最大值,EPS减载和柔性基础会使最大峰值与洞顶中心点数值的差距减小;拱形截面明洞洞顶同一平面竖向土压力呈现先减小、最后趋于稳定的趋势,最大值出现在明洞洞顶中心点。矩形截面明洞洞顶同一平面土体沉降曲线由减载前的“双V”型变化为减载后的“U”型。随后,对试验过程进行数值模拟分析,两者计算结果平均误差为11.0%,验证了试验数据的正确性及计算参数的合理性。最后,从填土横向应力上探讨了不同截面、基础刚度的明洞减载结构土拱效应的差异。

     

    Abstract: The high-filled open cut tunnel causes larger force applied on the structure and endangers its safety. Considering EPS induced load reduction, section type and foundation stiffness, the change rules of earth pressure and soil displacement on the top of open cut tunnel varying with the filling height are studied by model test and numerical simulation. The results show that the change of earth pressure on top of the load relieving structure of highfilled loess open cut tunnel is of nonlinear with filling height, the open cut tunnel with arched section is better than the rectangular one and the open cut tunnel with flexible foundation is better than that with rigid foundation regarding the load relieving effect; the earth pressure increases at first and decreases later and finally tends to be stable from the center at top to the two sides of open cut tunnel with rectangular section, the peak earth pressure occurs at the boundary of both sides of open cut tunnel, the difference between the peak earth pressure and the earth pressure at the central point of tunnel crown decreases due to the EPS induced load relieving and flexible foundation; the vertical earth pressure decreases at first and tends to be stable from the center to the two sides of open cut tunnel with arched section and the peak earth pressure occurs at the central point of tunnel top. The curve pattern of soil mass settlements at the top of the open cut tunnel with rectangle section changes from the "double V" before load relieving to the "U" distribution after load relieving. A numerical simulation analysis on the test process is conducted, and the average error of the two calculation results is 11.0%, which validates the correctness of the experiment data and the rationality of the calculation parameters. Finally the differences of soil arch effects of the load relieving structures of open cut tunnels with different section types and foundation stiffnesses are discussed in terms of lateral stress of fillings.

     

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